1. Field of the Invention
This invention relates to cooling devices and methods that use endothermic chemical and/or physical reactions to provide a heat sink. As a particular application, it relates to cooling methods and devices for injured body parts or severed extremities.
2. Description of the Prior Art
Various types of devices that use endothermic reactions for cooling purposes are known. For example, U.S. Pat. Nos. 3,095,291 and 2,898,744 granted to Robbins disclose respectively a "COOLING ENVELOPE WITH BREAKABLE DIAPHRAGM" and a "CHEMICAL FREEZING PACKAGE". U.S. Pat. No. 3,429,315 granted to McDonald discloses a "CHEMICAL REFRIGERANT BLANKET". U.S. Pat. 4,049,408 granted to Patel for a "DISPOSABLE COLD PACK FOR BLOOD SPECIMEN" is of particular interest because it discloses a device that maintains a blood sample at a temperature of 28 to 40 degrees Fahrenheit with no risk of subcooling below the critical lower temperature.
Devices designed specifically for cooling severed body parts are also known. Examples of such devices are described and illustrated in U.S. Pat. No. 4,723,974 dated Feb. 9, 1988 and granted to Ammerman for a "TRANSPORTING CONTAINER FOR AN AMPUTATED EXTREMITY".
Ammerman discloses a container consisting of an inner compartment surrounded by an exterior compartment. The exterior compartment is divided into two portions by a frangible separating barrier. One portion contains one part of a cooling medium such as water. The other portion contains another part of the cooling medium such as ammonium nitrate. Physical deformation of the flexible container breaks the frangible barrier and thus results in mixing together of the contents of the two portions.
Ammerman also discloses a container having a plurality of cooling bags in the exterior compartment each separated into two portions by a frangible barrier. Instructions are provided to the user of the container specifying when to break the barriers to maintain adequate cooling. Also disclosed is essentially the same device with a plurality of portions in each cooling bag. This design prevents the accumulation of granulated ammonium nitrate into one particular location and thus helps to effect a more even distribution of the cooling effect across the container assembly. In particular, an objective of this design was to prevent "hot spots" in which certain areas of the inner compartment would not be adequately cooled.
German Offenlegungsschrift No. 23 05 504 discloses a cooling bag that includes a chemical used as a thermal buffer.